Key principles
■ Snakebite is a potential medical emergency and
should always receive high priority assessment and
treatment, even if the patient appears initially well.
■ The majority of snakebites will not result in significant
envenomation and will not require antivenom.
■ Particular attention should be given to the patient
with a history of multiple bites. In most of these
cases major envenomation will occur, requiring
increased amounts of antivenom.
■ Admit all cases of probable snakebite for at least 12
hours after the bite or after removal of effective first
aid to a suitable clinical unit such as emergency, high
dependency or intensive care.
■ No patient with suspected snakebite should be
discharged in the evening or during the night or to a
situation where no other adult is able to observe the
individual over the following 24 hours.
■ Manage cases only in hospitals appropriately
equipped with laboratory facilities on-site and
adequate stocks of appropriate antivenom.
■ If the patient requires transfer to a higher level of
care then ensure this is organised early in the patients
presentation.
3.1 Snakebite envenomation
Major problems may include one or more of the
following effects of the venom (note these are principally
systemic rather than local effects):
Paralysis: blocked transmission at the neuromuscular
junction causing skeletal and respiratory muscle flaccid
paralysis, either presynaptic and/or postsynaptic. Signs
include: ptosis (drooping of upper eyelids), diplopia
(double vision), ophthalmoplegia (partial or complete
paralysis of eye movements), fixed dilated pupils,
weakness and respiratory problems.
Figure (1) Ptosis following Tiger Snake bite
Figure (2) Ptosis and partial gaze paralysis followingDeath Adder bite
Coagulopathy: cause includes defibrination with low
fibrinogen, unclottable blood but usually normal platelet
count, or direct anticoagulation, with normal fibrinogen
and platelet count. Both types cause elevated prothrombin
ratio (INR). Signs include: bleeding from bite wound,
venepunctures, rarely haematemesis and haematuria.
Figure (3) Oozing Venepuncture Site
PAGE 8 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
Snakebite
SECTION 3
Myolysis: caused by generalised destruction of skeletal
muscle with high serum CK (creatine kinase) and
myoglobinuria (red to brown urine testing positive for
blood; can be confused with true haematuria),
occasionally severe hyperkalaemia. Signs include: muscle
movement pain or weakness, and red or brown urine.
Figure (4) Myoglobinuria
Renal damage: primary or secondary (myolysis,
coagulopathy) acute renal failure. Signs include: oliguria
(decreased urine output) or anuria (no urine output).
General symptoms: include anxiety, headache, nausea,
vomiting, abdominal pain, collapse and convulsions.
Local symptoms: vary from minimal to obvious bite
marks, local pain, swelling, or bruising. A trivial-looking
bite site does not mean a trivial bite.
NB: Punctures or scratches may occur on the skin.
3.2 First aid
Pressure Immobilisation Bandage (PIB) and Splint:
■ Maintain airway/breathing if impaired
■ Immediately apply a broad compressive bandage to
the bite site at same pressure as for a sprain
■ Extend the bandage to cover the whole of the bitten
limb including fingers/toes
■ Splint limb and immobilise
■ Keep the patient still and bring transport to the
patient
■ Do not give alcohol, food, stimulants, or cut the
wound, or use a tourniquet.
■ DO NOT WASH OR CLEAN THE WOUND
■ Leave PIB in place until patient arrives at a place of
definitive care (hospital with appropriate antivenom etc).
■ As soon as possible after applying first aid as above,
notify the relevant doctor or hospital, to organise
medical evacuation.
■ If the snake was brought with the patient, place it in
alcohol (if practical), and ensure it goes with the
patient when evacuation occurs.
Figure (5a) Pressure immobilisation bandaging
Figure (5b) Pressure Immobilisation Bandaging
Figure (5c) Pressure immobilisation bandaging
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 9
3.3 Hospital cllinical assessment
3.3.1 History
1. Establish whether the patient has a
confirmed/witnessed snake bite (single or multiple)
OR were the circumstances such that a bite mighthave occurred:
2. When the patient was bitten (elapsed time)
3. Description of snake if possible (colour, length)
4. Geographic location that the incident occurred
(snakes in area)
5. Timing and type of first aid, and activity, following
the bite
6. Type and timing of symptoms, in particular:
a headache
b nausea
c vomiting
d abdominal pain
e blurred or double vision
f slurring of speech
g muscle weakness
h respiratory distress
i bleeding from the bite site or elsewhere
j passing dark or red urine
k local pain or swelling at the bite site
l pain in lymph nodes draining the bite area (axilla,
or groin),
m loss of consciousness and/or convulsions.
7. Relevant past history – specifically ask about allergy
or past exposure to antivenom, atopic (allergy)
history, renal, cardiac, or respiratory disease and
medications (eg. anticoagulants etc).
3.3.2 Presentation scenarios
■ Possible or definite snakebite.
■ The patient presents unwell, diagnosis uncertain.
There is a history of possible exposure to snakes (i.e.
walking in long grass etc), and the patient has any of
the following: loss of consciousness, convulsions,
headache, vomiting, weakness or paralysis (initially
ptosis, diplopia, slurred speech), dark or red urine,
bleeding, renal failure then consider snakebite.
■ The patient is unwell and may be envenomated.
■ The patient is well with no apparent envenomation.
3.3.2 Clinical assessment
Assess the patient for the following:
■ Evidence of a bite (if an adequate first aid bandage is
in place cut the first aid bandage away from over bite
site and the area immediately surrounding the bite)
■ DO NOT WASH THE WOUND – SWAB FOR VENOMDETECTION using the Snake Venom DetectionKit (SVDK) (refer to the SVDK section at page 11 in
these guidelines for technique of venom detection).
Examine for evidence of multiple bites, or venom
movement (eg. swollen or tender draining lymph nodes)
■ Neurotoxic paralysis (ptosis, ophthalmoplegia, diplopia,
dysarthria, limb weakness, respiratory distress)
■ Coagulopathy (bleeding gums, prolonged bleeding
from venepuncture sites or other wounds, including
the bite site)
■ Muscle damage (muscle tenderness, pain on movement,
weakness, dark or red urine indicating myoglobinuria)
■ Oliguria, anuria, or myoglobinuria
■ Period of unconsciousness or fitting
■ General symptoms such as headache, vomiting,
abdominal pain, but beware of these in isolation (i.e.
anxiety reaction only). If all other clinical and
laboratory indicators are normal, such general
symptoms alone are not usually sufficient reason to
commence antivenom therapy
3.3.3 Systemic envenomation
If it is evident that Antivenom Therapy will be required
then refer to the Antivenom Administration section at
page 22 in these guidelines).
Systemic envenomation is present if there is one or more
of the following:
■ Neurotoxic Paralysis (e.g. ptosis, ophthalmoplegia,
limb weakness, respiratory effects)
■ Significant Coagulopathy (e.g. unclottable blood,
INR>2, prolonged bleeding from wounds and
venepunctures)
■ Significant Myolysis (myoglobinuria)
■ Unconsciousness or convulsions
Early non-specific symptoms such as headache, vomiting,
abdominal pain may indicate developing envenomation.
Beware of these as purely manifestations of anxiety
rather than envenomation. If these are the only evidence
of envenomation then be cautious in deciding if
antivenom is required.
PAGE 10 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
3.4 Snake Venom Detection Kit (SVDK)
The SVDK is designed to detect very small amounts of
snake venom, and indicate which type of venom is present,
corresponding to one of the 5 monovalent antivenoms. It
does not necessarily indicate if envenomation has occurred.
Specifically:
■ Only use the SVDK to choose which antivenom is
appropriate
■ Do not use it to determine if there is envenoming, or
exclude snakebite
■ The best sample is a bite site swab (pre-moistened in
supplied SVDK fluid):
– Cut away bandage over bite site and swab for
venom detection
– Collect at earliest opportunity after presentation
to hospital
– Where systemic envenoming is evident then urine
may be used
– NB: Blood testing is unreliable
■ The test may take up to 25 minutes and is best
performed in a laboratory
■ A positive result in an envenomed patient indicates a
definite snakebite and the type of antivenom to use
(if required)
■ A positive SVDK is not the sole indication to give
antivenom
■ Administer antivenom if there is clinical and/or
laboratory evidence of significant systemic
envenoming indicated by the clinical signs and
symptoms listed
■ NB: Positive venom detection from the bite site does
not imply systemic envenoming and is not in itself an
indication for antivenom
■ A negative result does not exclude either a snakebite
or systemic envenoming
■ Always confirm the SVDK result by comparing with
result from diagnostic algorithms as outlined in Figure
(12) combined with knowledge of snakes in region
3.4.1 Snake venom detection kit testing
The SVDK comes in a kit including three separate test
well strips, each in protective foil, but only one set of
instructions, reagents and accessories. It must be kept
refrigerated, though if in a lab at 22ºC, it can be left out
of the fridge for the 20–25 minutes required to perform
the test.
Figure (6) Snake Venom Detection Kits
1. The best sample is a swab from the bite site. Take an
unused sample diluent bottle (currently yellow top)
and use fingernail to lever off the dropper cap.
2. Moisten the swab stick provided, in the solution in
the bottle. Rub the swab firmly over the bite site and
adjacent skin.
Figure (7) Swab bite site and adjacent skin
3. Place the end of the swab back in the bottle
containing solution and twirl around for a few
moments to transfer venom into solution. Then
proceed to use the kit as indicated in the instructions.
4. A positive result is indicated by a colour change (to
blue) in one of the first five wells, plus the positive
control well (well 7), within 10 minutes in the last
stage of the test. Observe all tubes carefully
throughout this last 10 minute period to identify the
first well to change colour. If one tube changes
colour, all will do so eventually, but only the first tube
to change is relevant.
Figure (8) Positive venom detection
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 11
5. A positive result usually indicates that:
■ venom was present on the skin
■ the type of snake involved
■ the appropriate monovalent antivenom to use should
this be needed
6. A positive SVDK result does not indicate systemic
envenomation and is not an indicator for antivenom
therapy.
7. A negative SVDK result does not exclude snakebite
(see these Guidelines on each type of snake for
further guidance on interpretation).
8. Be aware that false positives from bite site swabs,
though rare, are possible.
9. If the patient has evidence of systemic envenoming
and the bite site is not available for testing (i.e. been
washed, or not apparent), then URINE is worth
testing for venom. See kit instructions for dilutions, if
necessary. Do not test urine unless the patient has
evidence of systemic envenoming. Do not try and use
the SVDK to test on urine as a method of proving or
excluding snakebite. Urine can give false positives for
venom, especially brown snake venom. A positive SVDK
result for brown snake venom, in the absence of
clinical or laboratory evidence of envenoming, such
as coagulopathy, in nearly all cases should be
considered a false positive and therefore of no
diagnostic value.
10.Blood has proved an unreliable sample for venom
testing with the SVDK, giving both false positives and
false negatives. It is not recommended for use with
the SVDK.
11.The SVDK should not be used to determine if a
snakebite is a likely diagnosis. The only purpose ofthe SVDK is to determine best choice ofantivenom, should antivenom be indicated onclinical or laboratory grounds.
Figure (9) Snake/well correlation
Well 1 Tiger Snake Venom
Well 2 Brown Snake Venom
Well 3 Mulga Snake Venom
Well 4 Death Adder Venom
Well 5 Taipan Venom
Well 6 Negative Control
Well 7 Positive Control
Well 8 Blank Well
PAGE 12 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
Weak positive well 1 (cross-linkage effect, not relevant)
Strong positive well 3 = mulga snake
Weak positive well 5 (cross-linkage effect, not relevant)
Negative control well (6)
Positive control well (7)
Figure (10) Actual SVDK result in a case of Mulga Snake bite — CSL Snake venom detection kit
Figure (11) Common patterns of SVDK venom detection results
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 13
Well number:
1 2 3 4 5 6 7 8
Diagnostic pattern:
Only well 7 positive: No snake venom detected.This result does not include snakebite.
Wells 7 and 1 positive: If systemic effects includedefibrination, paralysis ± myolysis, suggests Tiger Snake orRough-scaled Snake bite. If systemic effects defibrination only, consider bite by Broad-headed, Pale-headed or Stephen’s Banded Snake. If systemic effects are confined to paralysis, without defibrination, consider possibility of Copperhead Snake.
Wells 7 and 2 positive: Most likely a Brown Snake bite. If systemic envenoming develops, expect defibrinationcoagulopathy, ± renal damage. Paralysis is unlikely andmyolysis should not occur.
Wells 7 and 4 positive: Death Adder bite. If systemic envenoming develops, expect post-synaptic paralysis, no coagulopathy, significant myolysis or renal damage.
Wells 7 and 5 positive: Taipan or Inland Taipan bite; systemic envenoming very likely. Expect defibrination, coagulopathy, paralysis, ± myolysis, ± renal damage.
Wells 7, 1 and 3 positive: This pattern is sometimes seenwith bites by several species. With a Copperhead bite, if there is systemic envenoming, expect paralysis withoutcoagulopathy. If a Red-bellied or Blue-bellied (Spotted) Black Snake bite, if there is systemic envenoming, expect only mild myolysis, no coagulopathy, paralysis or renal damage. If a Collett’s Snake bite, if there is systemic envenoming, expect myolysis, possibly anticoagulant coagulopathy, ± renal damage.
Wells 7 and 3 positive: Most likely a bite by a Mulga Snake (King Brown) or Collett’s Snake. If systemic envenoming, expect myolysis, extensive swelling of bitten limb, ± anticoagulant coagulopathy, ± renal damage, OR possibly a bite by a Red-bellied or Blue-bellied (Spotted) Black Snake. If systemic envenoming, expect only mild myolysis, no coagulopathy, paralysis or renal damage.
Figure (12) Methods for determining type of snake if venom detection is not available or has failed
PAGE 14 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
Determining the most likely snake based on clinical findings
Start here Local effects of bite
Examine the bite site
Minimal local effects, no significantredness, swelling, bruising
Obvious redness, swelling, ± bruising
Moderate to severelocal pain
Minimal or no local pain
Marked swelling after3+ hours
Only mild swellingafter 3+ hours
• ? Death Adder• Brown Snake• ? Taipan
• Mulga Snake• Red-bellied Black Snake• Yellow-faced Whip Snake
• Tiger Snake• Rough-scaled Snake• ? Taipan
Please note: This chart cannot cover all possible situations and assumes an understanding of the symptoms and signs of local, general and specific envenoming by Australian snakes. If in doubt, seek advice from the Poisons Information Centre (131 126) and from your local Critical Care Referral Network. © 1998 Dr Julian White
Combine this information with the result of the systemic effects key (below) to give a best guided estimate for the type of snake most likely to have caused the bite. Accuracy can be improved by matching this with known snake fauna for the region where the bite occurred.
Yes
Yes
Yes
Yes
Yes
No
No
NoNo
NoNo
Is there a coagulopathy?
Is there paralysis?
Defibrinationcoagulopathylow fibrinogenraised FDP/XDP
Anti-coagulationnormal
fibrinogenand FDP/XDP
Is there paralysis± myolisis?
Is thereparalysis?
• Brown Snake• Broad-headed Snake or Stephen’s Banded Snake
• Tiger snake• Rough-scaled snake• ? Taipan
• Mulga Snake• Spotted Black Snake• Collett’s Snake
• ? Death Adder• ? Copper- head
• Mulga Snake• Spotted Black Snake• Collett’s Snake• Small-eyed Snake
• Red-bellied Black Snake• Yellow-Faced Whip Snake
Is there majormyolysis?
Is there majormyolysis?
Systemic effects of bite
3.5 Laboratory evidence of envenomation
Laboratory testing in cases of possible snakebite is crucial
in diagnosis and is urgent. Any delay in delivering results
may delay definitive and life saving treatment. Frequent
repeat testing is almost always required. This is to ensure
that delayed envenoming or failure to respond to initial
treatment is not missed.
3.5.1 Laboratory testing
■ Laboratory tests to monitor for envenoming should
include coagulation studies (INR, aPTT, fibrinogen,
d-dimer), FBC/CBP (including blood film examination
for schistocytes), EUC and CK. (Where direct
fibrinogen testing is possible, down to very low levels
of fibrinogen, this is also a useful test).
■ If initial tests are normal, repeat testing at least twice,
at approximately 2–3 hour intervals, or more urgently
if the patient develops clinical evidence suggestive of
envenoming.
■ Where laboratory testing is not rapidly accessible a
whole blood clotting time (WBCT) may be performed
but should not delay arrangements for transfer of the
patient. (WBCT – put 10 ml venous blood into a glass
test tube and measure time taken to clot – normal
less than 10 mins).
■ An INR>2 indicates a coagulopathy (unless the
patient is on Warfarin).
■ Myoglobinuria or a significantly raised CK indicates
myolysis.
■ Abnormally raised creatinine or urea indicates renal
damage.
■ Cut away the bandage over bite site and swab for
venom detection (CSL Snake Venom Detection Kit).
■ The best sample for venom detection is a bite site swab.
3.5.2 Clinical and laboratory profiles following Australian snakebite
1. Defibrination coagulopathy
No paralysis or myolysis. The bite site usually has minimal
or no pain, no significant swelling, bruising or redness,
but there may be ooze of blood. Likely snakes include:
■ Brown Snakes (all species except Ringed Brown
Snake) (Genus Pseudonaja)
■ Broad-headed Snakes, including Stephen’s Banded
Snake and Pale-headed Snake (Genus Hoplocephalus)
2. Defibrination coagulopathy + paralysis ± mildmyolysis
Bite site is variable and there may be an ooze of blood.
Likely snakes include:
■ Taipan and Inland Taipan (Genus Oxyuranus).
3. Defibrination coagulopathy + paralysis +moderate to severe myolysis
Bite site is usually painful with mild swelling, bruising,
redness, and there may also be an ooze of blood. Likely
snakes include:
■ Tiger Snakes (Genus Notechis)
■ Rough-Scaled Snake (Genus Tropidechis)
4. Moderate to marked myolysis + anticoagulantcoagulopathy (fibrinogen normal, no raisedFDP/XDP)
No paralysis (beware major myolysis mimicking paralysis).
Bite site is usually painful, often with marked swelling
and sometimes bruising. Persistent blood ooze is not
common. Likely snakes include:
■ Mulga snake, Collett’s snake, Spotted black snake
(Genus Pseudechis).
5. Moderate to marked myolysis
No paralysis (beware major myolysis mimicking paralysis)
or coagulopathy. Bite site is usually painful, has marked
swelling and sometimes bruising. Persistent blood ooze
not common. Likely snakes include:
■ Mulga snake, Collett’s Snake, Spotted Black Snake
(Genus Pseudechis).
■ Eastern Small-Eyed Snake (Rhinoplocephalus
nigrescens).
6. Paralysis (postsynaptic: reverses with antivenomtherapy) ± mild anticoagulant coagulopathy
No myolysis and renal damage unlikely. Bite site is often
painful, but with little swelling, redness or bruising.
Persistent blood ooze unlikely. Likely snakes include:
■ Death Adders (Genus Acanthophis).
7. General symptoms of envenomation (some or allof: headache, nausea, vomiting, diarrhoea,abdominal pain, dizziness, collapse).
No paralysis or coagulopathy with no, or generally mild,
myolysis. Bite site is usually painful with marked swelling
and sometimes bruising. Persistent blood ooze not
common.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 15
Likely snakes include:
■ Red-bellied Black Snake (Pseudechis porphyriacus)
and mild bites by Spotted Black snake and Collett’s
Snake (Genus Pseudechis).
■ Yellow-faced Whip Snake and other large Whip
Snakes (Genus Demansia).
3.6 Essential information for hospitallaboratory staff
Details of venom actions and venom profiles for each
major snake species are contained in these guidelines and
should be referred to when interpreting laboratory results.
3.6.1 Required laboratory testing
1. Coagulation Studies: PT/INR, aPTT, fibrinogen level,
d-dimer/FDP, platelet count (Where direct fibrinogen
testing is possible, down to very low levels of
fibrinogen, this is also a useful test).
a. Defibrination-type coagulopathy (BrownSnakes,
Tiger Snakes, Rough-scaled Snake, Taipans, Broad-
headed Snake group).
■ Characterised by grossly prolonged PT & aPTT,
undetectable fibrinogen, grossly elevated d-dimer/
FDP, platelets normal (sometimes slightly low).
■ Some coagulation machines will have trouble
giving results in this situation. If the machine
indicates gross prolongation of PT/aPTT, but
fibrinogen “very high”, this usually indicates
undetectable fibrinogen.
■ If d-dimer/FDP is elevated, you can be sure
fibrinogen will be very low, not very high. As soon
as such a picture is evident, immediately report
this to the treating doctor.
■ Do not delay while trying to get final results from
the machine. Similarly, if d-dimer/FDP is elevated,
report this first, then go back and determine the
actual level, which may take time.
■ Do not waste valuable time retesting and calling
for new specimens because the machine cannot
cope with the grossly abnormal results. Snakebite
coagulopathy is common and time is of the
essence. So, look for the typical defibrination
picture and report this as soon as it is clear that it
is present. Be aware that in mild cases, in the
early stages, PT/INR and aPTT may be normal,
fibrinogen level normal or only slightly decreased,
but d-dimer/FDP will be elevated.
■ This is an important indication of possible
developing coagulopathy. However, a similar
picture is present in a patient with venous
thrombosis problems, so careful clinical judgement
will be required by the treating doctor, to decide
which is the more likely diagnostic explanation.
b. Anticoagulation-type coagulopathy (Mulga
Snakes, Collett’s Snake).
■ Characterised by mild to grossly prolonged PT and
aPTT, but normal fibrinogen levels and no significant
elevation of d-dimer/FDP.
c. Patients on Warfarin and similar anticoagulants
■ These patients may present a problem in interpreting
results, if bitten by a snake. Warfarin should cause
prolongation of PT in particular, sometimes with
elevated d-dimer/FDP, but normal fibrinogen. If
snakebite defibrination coagulopathy is overlaid
on this background, in most cases, fibrinogen will
be depleted and d-dimer/FDP grossly elevated, with
an INR of >4, usually >10 (actually infinity). This
should not cause confusion in interpretation, as
such a pattern is clearly not due to Warfarin, but a
result of envenoming.
■ This pattern may be complicated by the fact that
warfarin causes low levels of factors, which the
toxins need to act on, leading to different
pharmacodynamics.
■ In cases with early or mild snakebite defibrination
coagulopathy, changes may be subtle. In this
setting, significant elevation of d-dimer/FDP may be
the most important diagnostic clue that envenoming
is occurring. In cases of snakebite anticoagulation-
type coagulopathy, interpretation may be more
difficult, as elevation of d-dimer/FDP is not a feature.
In this setting coagulation tests may not give clear
cut evidence of envenoming. Fortunately, in these
cases, clinical features and rising CK are likely to
assist in diagnosis of envenoming.
2. Complete blood picture (Platelets, Hb, WCC,
absolute lymphocyte count, including blood film
examination for schistocytes).
a. Acute systemic envenoming usually causes an
elevated WCC
b. There may be an associated absolute lymphopenia,
which can be quite marked
c. Lymphopenia is always present in tiger snake bites
with systemic envenoming, but is less consistent for
other snake species
PAGE 16 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
d. Thrombocytopenia is not a common acute feature of
envenoming and when present, is often associated
with renal damage
e. In rare cases, especially with Brown Snake bite, a
thrombocytopenia like picture may develop, often
after the initial defibrination coagulopathy is
responding to antivenom. In such cases there will be
a falling Hb, falling platelet counts, rising creatinine
and urea, and usually schistocytes on the blood film.
3. Muscle Function (CK)
a. A number of snakes can cause moderate to severe
systemic muscle destruction (myolysis) including
Mulga Snakes, Collett’s Snake, Tiger Snakes, Rough-
scaled Snake, Taipans and Black Snakes).
b. This may take several hours to become evident,
occasionally days.
c. Clinically the patient develops muscle pain, weakness
and myoglobinuria. At a lab level, CK can become
grossly elevated.
d. Significant myolysis is associated with CK levels
>1,000 IU/L and can exceed 100,000 IU/L (sometimes
far higher than this). In such cases beware associated
hyperkalaemia that can cause lethal cardiac toxicity.
e. Measurement of serum or urine myoglobin levels does
not add to the diagnosis, is expensive, and treating
doctors should be encouraged to use CK levels as the
indicator of myolysis rather than myoglobin levels.
4. Renal function (creatinine and urea)
Snakebite can cause renal damage and occasionally renal
failure, often secondary to coagulopathy, myolysis, or
hypotension. In mild cases, especially with brown
snakebite, there may be a slow rise in creatinine and
urea over the first few days, without polyuric or anuric
renal failure, which will reverse and gradually improve
over a week or so. However, rising creatinine and urea
should always be flagged, as it may indicate progression
to major renal failure.
5. Electrolytes
Hyperkalaemia is the major risk, most often in
association with myolysis and secondary renal failure.
However, hyponatraemia can also develop, most likely in
response to over vigorous IV fluid replacement.
6. Liver function tests
a. LFTs are not routine tests in snakebite cases.
Temporary elevation of LFTs sometimes occurs but is
rarely of clinical significance
b. There is no defined picture of envenoming-induced
liver damage in humans. However, LDH is a useful
test in patients with haemolysis, either in Brown
Snake bites that develop microangiopathic haemolytic
anaemia or in Black Snake where direct toxin
mediated haemolysis may occur.
3.2.1 Derived fibrinogen (important considerations)
Derived fibrinogen is merely a reflection of the PT and as
such adds nothing more than a pseudo PT and is not as
sensitive as a direct Fibrinogen (Clauss). This is poorly
recognised with many laboratories not clearly
distinguishing derived vs direct (Clauss), while others
report both derived and Clauss.
Furthermore, there is a limit of quantification/reporting
for Clauss fibrinogen, because this differs on machines
and most importantly in the way they are reported or
understood by the laboratory staff.
Some analysers will only allow results such as <0.65, and
it is impossible to get anything lower. This is not very
sensitive because by the time the Fibrinogen is above
0.65 the PT/aPPT have usually started to recover.
In some laboratories the limit of quantification is <0.5,
however they will often report 0.2 or 0.3 but say it is
below the limit of quantification (not detection) so they
can’t guarantee the difference.
This is an important difference in those reports below
the LOQ and the LOD, which may not be clear to some
laboratories.
The issues around low levels of Fibrinogen are complex,not necessarily well understood and are often limited bythe analyser only reporting <LOQ. This is primarily due tothe broad acceptance that a Fibrinogen <1.5 is low andoften associated with significant haematologicalabnormality. However, treated snake bite patients havevery low Fibrinogens which are actually recovering, buttake time to get >1.5. For these patients it is importantto know that the Fibrinogen is just detectable.
It is also common to find a “near normal” PT/aPTT whenthere is still a low Fibrinogen around 0.5 – 0.9. This is aproblem for the analyser and may not be understoodwell by Haematologists who are not familiar with resultsdemonstrating a slightly raised INR and a low Fibrinogen.
It is suspected, but not yet proven, that in snake bite thePT is driven by factor V deficiency (and also factor VIII),and not so much by fibrinogen – the former recoversmore rapidly, which is manifested by a normalisation of
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 17
the PT and a gradual recovery of fibrinogen. This is likelyto be the main driver for the use of Fresh Frozen Plasma(FFP) in these situations.
Given the complexity of interpreting derived Fibrinogen
and very low Fibrinogen levels in these patients, it is
strongly recommended that early expert advice be
obtained in the first instance through the PoisonsInformation Centre on phone 131126.
3.7 Hospital clinical management
Venomous snakebite is a medical emergency, potentially
life threatening, and is not a simple matter of just giving
antivenom. Expert advice is available from the PoisonsInformation Centre on phone 131126 and through
the local Critical Care Referral Network.
A considerable number of snakebites do not result in
significant illness, and do not require antivenom, but all
probable snakebites should be admitted for observation
for at least 12+ hrs or overnight, as some serious effects
may be delayed.
Following the immediate clinical management, the
definitive clinical management will be dependant upon
whether or not the health facility has antivenom stocks
immediately available.
3.7.1 Immediate clinical management
■ Assess and maintain airway
■ 100% Oxygen
■ Respiratory support as indicated
■ Establish intravenous access and administer
intravenous fluids (fluid load)
■ Commence serial clinical observations and serial
laboratory testing. If clinical (including antivenom
stocks) or laboratory facilities are inadequate,
maintain pressure immobilisation bandage and
arrange retrieval to an appropriate hospital
■ Antivenom therapy is indicated in most cases if there
is any evidence of systemic envenoming detected by
clinical observation or on laboratory testing
■ Consult early with the local Critical Care Referral Network,
Clinical Toxicologist and the Poisons Information
Centre preferably before commencing antivenom
■ Removal of pressure immobilisation bandage:
– The bandage should not be removed until the
patient is fully assessed (clinical history,
examination, laboratory tests performed and
results assessed, venom detection performed and
result obtained), stabilised (ABC, IV line in situ, IV
fluid load) and if envenomed, treatment commenced
(appropriate type and dose of IV antivenom given).
– In a significant number of patients, initial clinical
and laboratory examination will be normal, with
no indication of systemic envenoming. Such
patients do not require antivenom at this time
and the pressure immobilisation bandage first aid
should be removed.
– The patient should then be fully re-evaluated
within 2 hours (including repeat laboratory
testing) or earlier if symptoms develop.
– Do not leave pressure immobilisation bandage in
place for long periods of time, especially in an
asymptomatic patient.
3.8 Clinical management of definiteor probable snakebite in a hospitalwithout antivenom available
Where the patient presents with a definite or possible
snakebite.
1. If not already applied, immediately apply correct first
aid, namely a broad compressive bandage bound first
over the bite site, at the same pressure as for a sprain
(i.e. not so tight that it occludes the blood supply),
then bind the bandage over as much of the bitten
limb as possible, going over the top of clothing, and
keeping the limb as still as possible.
2. Once the limb is bandaged then immobilise it using a
splint and keep it in a neutral position (not elevated
or below the patient).
3. Do not wash the wound, but if a venom detection kit
is available then swab the wound prior to applying
first aid, but do not delay first aid significantly just to
swab for venom, unless the patient appears well and
greater than 20 minutes has elapsed since the bite.
4. Keep the patient as still and quiet as possible.
5. Fast the patient, and be prepared for vomiting.
6. Carefully watch for evidence of envenoming, and if
there is respiratory distress then provide respiratory
support.
7. Monitor urine output and colour.
8. If the snake was brought with the patient, place it in
alcohol (if practical) and ensure it goes with the
patient when evacuation occurs.
PAGE 18 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
9. As soon as possible after applying first aid as above
and notify the relevant doctor or hospital to organise
medical evacuation. It will assist the retrieval team if
you can give the following patient status report:
■ Name, sex, age of patient
■ Brief history of the suspected bite
■ Was a snake seen?
■ What type of snake?
■ Was it a multiple bite?
■ Are there any symptoms or signs of envenomation?
(Namely: headache, nausea, vomiting, abdominal
pain, collapse, convulsions, early paralysis such as
drooping upper eyelids, double vision, slurred
speech, limb weakness, evidence of bleeding
problem such as persistent ooze from the bite
site, evidence of muscle damage such as dark or
red urine, muscle pain).
■ Patient’s past history, particularly past snakebites
with antivenom therapy, allergic disease, renal or
heart disease, or use of anticoagulant drugs
(e.g. warfarin) or anti-platelet drugs (e.g. aspirin
or NSAIDS).
3.9 Clinical management of definiteor probable snakebite in ahospital with antivenom available
3.9.1 Respiratory failure
Artificial ventilation – mouth to mask; bag/mask,
bag/endotracheal tube as indicated.
3.9.2 Circulatory failure
1. If cardiac arrest – commence cardiopulmonary
resuscitation.
2. Insert an IV line (normal saline, give initial IV fluid load,
500 – 1000ml over 2hrs in adults, 20ml/kg for children,
then run at maintenance, keep the patient fasted).
3. If possible insert long line in cubital fossa or similar,
to allow frequent blood sampling and avoid the need
for further venepunctures.
4. Avoid subclavian, femoral and jugular vessels, as
uncontrollable haemorrhage may occur if there is a
coagulopathy.
5. If profound hypotension – fluid and electrolyte
resuscitation.
6. A degree of hypertension may be encountered which
usually resolves.
If patient already has severe envenomation then apply
pressure bandage/ immobilisation first aid if not in situ
(remove only when initial antivenom therapy is completed).
3.9.3 Blood samples
1. Whole blood clotting time (in glass test tube)
2. Coagulation studies (PT/INR, aPTT, Fibrinogen, XDP/d-
dimerFDP) full blood profile (CBP/FBE including blood
film examination for schistocytes) (Where direct
fibrinogen testing is possible, down to very low levels
of fibrinogen, this is also a useful test)
3. Electrolytes, renal function, CK
4. Avoid venepuncture in sites where bleeding may be
difficult to control (i.e. femoral, neck, subclavian)
3.9.4 Anaphylaxis
Anaphylaxis due to allergy to venom is occasionally seen:
(i.e. in reptile keepers). Treat with IV Adrenaline infusion or
IM Adrenaline (initial dose 0.25–0.5 mg.). For suggested
paediatric dosages and further information, refer to the
relevant section in these guidelines.)
3.9.5 Ongoing care
1. Observe closely for evidence of developing paralysis
(ptosis and diplopia).
2. Monitor urine output – indwelling catheter as
necessary.
3. Serial respiratory function (FVC, O2 saturation and/or
expired CO2).
4. Check and update Tetanus immunisation status (once
coagulopathy has resolved).
5. Avoid unnecessary venepunctures.
6. Once the patient is stabilised the pressure.
immobilisation bandage may be removed however, if
the patient has a severe envenomation and requires
transfer to another hospital and/or if there will be a
delay in obtaining further supplies of antivenom,
consider leaving the pressure immobilisation bandage
in situ.
7. If left in situ, then regular limb circulation
observations should be performed.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 19
Figure (13) Snakebite management chart
PAGE 20 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
Patient presents with possible snakebite
Patient is severely envenomed, i.e. hasone or more of: collapse/unconscious,paralytic signs, coagulopathy, myolosis
Please note: This chart cannot cover all possible situations and assumes an understanding of the symptoms and signs of local, general and specific envenoming by Australian snakes (see Section 4: Snakebite, and preceding pages). If in doubt, seek advice from the Poisons Information Centre (131126) and from your local Critical Care Referral Network. © 1998 Dr Julian White
Patient is symptom-free, or has only mildor general symptoms, i.e. has one or more of:headache, nausea/vomiting, abdominal pain
FIRST AIDPatient has had correct
first aid appliedi.e. PIB
FIRST AIDNo effective first aid
has been appliedAPPLY PIB first aid
FIRST AIDPatient has had correct
first aid appliedi.e. PIB
FIRST AIDNo effective first aid has been
applied DO NOT APPLYnow if >1hr post-bite
Leave PIB in place until patient is stabilised,fully assessed, and antivenom given (if required)
Repeat blood tests at 3 hrs and 6 hrs post AV
Coagulopathy is resolving (rise in fibrinogen/reduction
in whole bloodclotting time)
Coagulopathy not resolving(no rise in fibrinogen/
grossly prolonged wholeblood clotting time
Develops or has significantsymptoms or signs or
abnormal blood tests, i.e. paralytic signs, coagulopathy,
myolysis, renal impairment
Remains symptom-free orminor general symptoms only(i.e. headache, nausea etc)and blood tests are normal;
do not give antivenom
Remove first aid once IV lineinserted, venom detection*and blood tests performed
and reported as normal
TREATMENT: Continue tomonitor closely; repeatblood tests to ensure
continuing improvement
TREATMENT: Once recovered, send home but follow up for serum sick-
ness. Consider prophylacticoral steroids for 1 week.
TREATMENT: Give moreantivenom IV, diluted,
adrenaline ready (in case ofanaphylacticoid reaction
TREATMENT: Give appropriateAntivenom IV, diluted,
adrenaline ready (in case ofanaphylactoid reaction
TREATMENT:Admit overnight. If remains
well, repeat blood tests next morning and ifnormal, send home.
TREATMENT:Check patient for signs of
envenoming frequently andrepeat blood tests after
about 2 hrs, then 2–3 hrs later
TREATMENT• Attend to ‘ABC’ but be careful of causing bleeding.• Insert IV line, given IV fluid load.• Take blood for lab tests* and swab bite site for venom detection** collect urine and check for haemoglobin/myoglobin (dip stick) and keep bite site swab for venom detection• Commence IV antivenom (use Polyvalent or mixture of monovalent AVs if snake identity is uncertain; do not delay giving AV by waiting for venom detection results)• Consider giving increassed starting doses of antivenom• Monitor fluid balance, catheterise if in doubt about urine output.
Patient discharged home
FIRST AID FOR SNAKE BITEPIB = Broad bandage over
bite site, then rest of bitten limb,including toes/fingers, at same
pressure as for ankle sprain,then splint limb, keep immobile.
Leave PIB first aid in placeuntil patient is stabilised
and antivenom given
Remains symptom-free or minor general symptoms only (i.e. headache, nausea etc) and blood tests are normal; do not give antivenom
*Laboratory testsCoagulationIf no lab quickly available:• Whole blood clotting time (QBCT) (5–10 ml venous
blood in glass test tube. Measure time to clot; >10 mins suggests coagulopathy but test staff member’s blood as normal control.
If lab available, request:• Prothrombin time/ INR • aPTT • FDP/XDP (d-dimer) • CBP/FBE (platelet count and blood film for schistocytes)Other• Creatinine and urea • Electrolytes (especially K+)• CK for myolysis • CBP/FBE (WCC for leukocytosis ± lymphopenia
• Insert IV line, given IV fluid load. • Take blood for lab tests. * • Cut away first aid bandage (if present) over bite site and swab bite site for venom detection. ** • Collect urine and check for haemoglobin/myoglobin (dip stick) and keep for for venom detection. • Secure supply of antivenom (use Polyvalent AV or a mixture of monovalent AVs if snake identity uncertain• Monitor fluid balance, consider catheterising if in doubt about urine output.
TREATMENT
SVDK SNAKE VENOM DETECTION KIT**Cut away first aid bandage over bite site only, to allow visual access and swab for venom detection. NOTE: bite site swab is best sample. Only test urine if no bite site
available AND patient has systemic envenoming. DO NOT use SVDK to determine if patient has snakebite.
3.11 Antivenom therapy
Antivenom is the definitive treatment of envenomation,
potentially life saving and is produced using refined
horse serum therefore it is potentially allergenic and as
such its use is not without risk. Therefore, antivenom
should only be used if there is systemic envenoming.
Overall, less than 1 in 4 patients require antivenom therapy.
3.11.1 Key antivenom therapy principles
■ The treatment of choice for systemic envenoming is
to use a monovalent (specific) antivenom in
preference to polyvalent antivenom if the identity of
snake is known.
■ Use the SVDK in conjunction with the diagnostic
algorithms along with consideration of the type of
snakes found in region to determine the most
appropriate antivenom therapy.
■ Consult with the NSW Poisons Information CentrePh: 131126 if unsure or if there is a conflict between
the SVDK and diagnostic algorithm results.
■ Do not overlook polyvalent antivenom as backup if
insufficient monovalent antivenom available.
■ 1 vial of CSL Polyvalent Snake antivenom isequivalent to 1 vial of relevant monovalentantivenom.
■ Dosage varies with the type of antivenom, type of
snake and number of bites however, childrenrequire the same dose as adults.
■ Further doses of antivenom may be required in major
cases.
3.11.2 Snake identified
Monovalent Antivenom is preferred to Polyvalent as it is
less hazardous and has fewer side effects, and is less
expensive. Refer to the relevant section on specific snake
management, in these guidelines, for the appropriate, safe
and effective administration of antivenom therapy. It must
be noted that bites by some snakes may not need anti-
venom even if there is mild to moderate envenoming.
3.11.3 Snake not identified
Where an SVDK is not available, or failed, or the patient
requires antivenom before a SVDK result is possible, then
either Polyvalent Antivenom or an appropriate mixture of
Monovalent Antivenoms should be used. Diagnostic
algorithms (Figure 12, page 14) may assist in choice of
antivenom. Refer to Appendix (1) to determine if there is
an appropriate mix of two monovalent antivenoms for
your area. In general terms, in eastern NSW, a mixture of
CSL Tiger Snake Antivenom and CSL Brown Snake Anti-
venom will often be appropriate, providing a bite from a
Death Adder can be excluded on grounds of description
of the snake. However, there are areas where such a mix
will not be sufficient, such as far North-Eastern NSW
where there is a chance of Taipans being present.
3.12 Antivenom therapy dose
The minimum dose is one vial of the appropriate
antivenom however for some antivenoms the initial dose
is higher.
Multiple bites or severe envenoming mandate higher
doses; increase the dose by 1 to 3 vials, depending on the
type of antivenom, and be prepared to give more. Four
to 6 or more vials is not unusual in a severe snakebite.
If there is a coagulopathy then the dose can be titrated
against serial coagulation results (see relevant section in
these or guidelines for managing coagulopathy).
3.12.1 Brown Snake
The starting dose for severe Brown Snake envenomation
is currently being investigated by a national multi-centre
prospective trial. The initial dose may range from 2 to 5
vials.
In small remote centres, the current recommended initial
dose in a life-threatening situation is 2 vials. Organise
medical retrieval as early as possible for the patient to be
immediately transferred to the closest Rural Referral
Hospital for ongoing management and additional doses
as required.
In Rural Referral and Tertiary Referral Hospitals sufficient
antivenom stocks will be available to give additional doses
as required and replenish stocks at the small remote centres.
As dosing recommendation may evolve with time,
consultation with a clinical toxicologist via the New
South Wales Poisons Information Centre Phone131126 is recommended in all cases.
3.12.2 Tiger Snake
Starting dose for a major bite is 4 vials of CSL Tiger
Snake Antivenom.
For some smaller rural hospitals, the recommended stock
level is only 2 vials, to be given in life-threatening
situations, whilst supplementation of stocks from another
hospital, plus medical retrieval, are being arranged.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 21
3.12.3 Taipan Snake
Starting dose for a major bite is 3 vials of CSL Polyvalent
or 3 vials of Taipan Antivenom.
3.12.4 Mulga Snake
Starting dose for a major bite is 1 vial of CSL Black Snake
Antivenom or 1 vial Polyvalent Antivenom.
3.12.5 Red-bellied Black Snake
Starting dose for a major bite is 1 vial of CSL Tiger Snake
Antivenom (not Black Snake Antivenom).
3.12.6 Death Adder
Starting dose for a major bite is 1 vial of CSL Polyvalent
or 1 vial Death Adder Antivenom.
As dosing recommendation may evolve with time,
consultation with a clinical toxicologist via the NewSouth Wales Poisons Information Centre, phone131126 is recommended in all cases.
3.13 Antivenom administration
Prepare the patient and clinical environment for potential
anaphylaxis or anaphylactoid reaction to antivenom.
3.13.1 Preparation prior to commencing antivenom
1. High flow oxygen.
2. Dedicate one small bore (18–20g in adults) IV line to
antivenom administration, and one large bore IV line
(16–14g in adults) for emergency resuscitation
(equivalent size suitable for children).
3. Prepare 1L Normal Saline (20 mL/kg in children) ready
to give under pressure.
4. Prepare adrenaline 1:1000 (1 mg in 1mL) drawn up to
a dose of 0.01 mg/kg (max. 0.3 mg, i.e. max 0.3 mL)
and label “Adrenaline for IM injection only (dose in mg)”.
5. Prepare an IV infusion of adrenaline 1 mg in 100mL
or as per local protocol (controlled by infusion pump
or syringe driver) ready to attach by a side arm to the
resuscitation line. Anti-reflux valves must be attached
above the side arm on any other infusions using this
IV, to prevent adrenaline going back up into the other
fluid bags. To prevent erroneous administration, do
not attach the adrenaline infusion unless it is needed.
6. Continuous monitoring of vital signs including ECG,
Pulse, BP and Sa02%.
7. Record blood pressures on the other side to the
fluid/adrenaline infusion, to avoid prolonged cuff
inflations and thus extravasation of infusion fluids.
3.13.2 Administration method
1. Antivenom for snakebite should always be given IV,
with all facilities ready to hand to treatanaphylaxis in the rare event that it should occur.
2. Intravenous fluids running.
3. Dilute the antivenom about 1:10 (1:5 or less may be
needed if volume is a problem, i.e. polyvalent
antivenom, paediatric patient), in IV fluid (e.g. normal
saline, or Hartmans).
4. Start infusion very slowly carefully observing patient
for reaction (look for flushing, rash, tachycardia,
hypotension, bronchospasm; in children warning
signs also include nasal, palatal, or ocular pruritis,
coughing, sneezing, profuse sweating, faecal or
urinary urgency or incontinence, abdominal pain, and
a sense of impending doom) and increase rate aiming
to give whole dose over 15 to 20 minutes.
5. If the patient has had 25 mLs or more Antivenom then
consider a 7-day course of prophylactic oral steroids.
6. Ensure snakebite patients are followed up adequately,
particularly if given Antivenom, watching specifically
for serum sickness.
3.13.3 Management of an anaphylactic reaction
1. Most reactions are related to the rate of antivenom
infusion.
2. Some mild reactions resolve with temporary cessation
of the antivenom infusion and recommencing
infusion at a slower rate.
3. Envenomed patients may be severely coagulopathic,
so caution must be observed when giving Adrenaline
to avoid blood pressure surges, which might lead to
intracerebral haemorrhage.
4. Initial management of severe reactions (sudden
hypotension, bronchospasm):
a. Suspend the antivenom infusion
b. Lie the patient flat (if not already), continue high
flow/100% oxygen and support airway/ventilation
as required
c. Rapid infusion of 1L Normal Saline (20 mL/kg in
children) over 2–3 minutes
d. Adrenaline IM into the lateral thigh, 0.01mg/kg to
maximum of 0.3 mg (observe puncture site for
PAGE 22 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
bleeding). Alternatively an IV Adrenaline infusion
may be used as per point 5b below
e. Liaise with toxicology service regarding ongoing
management
5. For reactions that do not respond to initial management:
a. If hypotensive, repeat Normal Saline bolus as
above (up to 50mL/kg may be required)
b. Commence IV infusion of adrenaline
(0.5–1mL/kg/hour, of 1mg in 100mL) and titrate
according to response; monitor BP every 3–5
minutes (using the arm opposite to the infusion);
beware that as the reaction resolves adrenaline
requirements will fall, the blood pressure will rise
and the infusion rate will need to be reduced
6. Consider nebulised salbutamol for bronchospasm,
nebulised adrenaline for upper airway obstruction,
and IV atropine for severe bradycardia.
7. Seek advice urgently from the local/regional ED
Consultant and/or ICU Consultant.
3.14 Snakebite coagulopathy
3.14.1 Defibrination
Some snakes may cause a significant coagulopathy as part
of envenoming (e.g. Brown Snakes, Tiger Snakes,
Rough-scaled Snakes, Broad-headed Snakes, Stephen’s
Banded Snakes, Taipans). This is due to potent
procoagulants in the venom, which in vivo cause
consumption of fibrinogen and fibrinolysis i.e.
Defibrination Syndrome.
This may occur rapidly following envenoming, within 30
to 60 minutes, with the blood being unable to clot.
Platelets are usually unaffected.
Snakebite coagulopathy can prove complex to manage,
and it is preferable to treat the patient in a major
hospital, with full coagulation laboratory facilities on site.
Tests for coagulopathy:
1. If there is no laboratory in your hospital, perform a
whole blood clotting time (5 to 10 mL venous blood in
a glass tube, e.g. test tube, and observe time to clot;
normal is less than 10 mins, if there is a coagulopathy
there will be no clotting at 15 minutes or only a very
weak clot). However, performing a WBCT is not a
substitute for laboratory coagulation tests and should
only be used as initial assessment while transfer to a
hospital with laboratory facilities is being organised.
2. Simultaneously take blood for later laboratory tests.
3. The most useful tests are: prothrombin ratio (INR),
aPTT, fibrinogen level, and fibrinogen degradation
products (XDP/d-dimer or FDP).
4. In some laboratories a thrombin clotting time (TCT)
may be useful to assess fibrinogen level.
5. A complete blood picture (CBP/FBE) should be
performed for platelet count.
6. In most cases, a single batch of tests will not be
sufficient, and serial studies will be needed.
Expected results in coagulopathy:
1. Whole blood clotting time will be greater than 15
minutes or there may be only a weak clot in less
severe cases (usually will not clot even after 1 hour) /
(normal = less than 10 minutes).
2. INR (prothrombin time) grossly prolonged (>4, usually
infinity) / (normal = 1.0).
3. aPTT grossly prolonged (>150 secs) / (normal = less
than 40 secs).
4. Thrombin clotting time (TCT) grossly prolonged
(>150 secs) (normal 15 secs).
5. NOTE: TCT may be the first parameter to show
improvement as a result of antivenom therapy,
dropping from >150 secs to less than 100 secs. If this
occurs it probably indicates that enough antivenom
has been given, despite the lack of improvement in
other parameters, therefore cease further antivenom
therapy and repeat tests in 1 hour to confirm trend
of improvement.
6. Fibrinogen level very low (<0.1g/L) / (normal = 1.5 to
4.0g/L). This is the key diagnostic finding in
defibrination coagulopathy.
7. Fibrinogen degradation products grossly elevated
(XDP/d-dimer > 16) / (normal = <0.25). This is
another key diagnostic finding.
8. NOTE: Degradation products are in themselves
anticoagulant, and at such high levels may interfere
with some clotting tests, giving falsely high levels of
abnormality, particularly INR and aPTT on some
automated coagulation machines. This may obscure
the first signs of recovery.
Management principles:
1. If initial studies are normal, remove PIB first aid and
repeat studies after 2 hours, or sooner if the patient
appears envenomed.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 23
2. If the second set of tests are also normal, repeat a
third time, a further 3 hours later.
3. If there is a significant coagulopathy (unclottable blood,
or INR>2 + low fibrinogen), then this must be treated.
4. Antivenom is the treatment of choice. Replacement
therapy with clotting factors (e.g. whole blood, FFP,
cryoprecipitate) should be avoided as it is liable to
make the coagulopathy worse if there is still active
venom. Once active venom is all neutralised by
antivenom normal homeostasis rapidly rectifies the
problem (sometimes within 3 hours), placing the
patient out of danger (i.e. INR <4), usually without
need of any other treatment.
5. Antivenom therapy can be titrated against the
resolution of the coagulopathy, in particular, the
fibrinogen level. After the initial dose of antivenom
retest clotting studies at 3 and 6 hours after
completion of antivenom dose. If still showing a non-
resolving coagulopathy at 6 hours (i.e. no significant
rise in fibrinogen level), it is usually necessary to give
more antivenom and repeat tests as above,
continuing this process until there is evidence of
resolution, but if there is no resolution after an
adequate initial dose, then expert advice should be
sought to determine further dosing, rather than
giving ever increasing amounts of antivenom.
6. NOTE: even if enough antivenom has been given,
many coagulation parameters will remain abnormal
for hours or days, especially fibrinogen degradation
products, which may remain elevated for 48 hours,
longer if there is renal failure. A rise in fibrinogen
level from zero to detectable is the key indicator of
resolution of the defibrination coagulopathy, not a
return to normal fibrinogen levels, which may take
many hours. In some laboratories, the first evidence
of such a rise may be a fall in the aPTT or INR, rather
than a change in detectable fibrinogen titres.
3.14.2 Anticoagulation
This occurs after some severe bites by Mulga Snakes,
Collett’s Snakes and possibly Spotted/Blue-bellied Black
Snakes and is due to direct anticoagulants in the venom,
which interfere with the extrinsic and, to a lesser extent,
the intrinsic clotting pathways.
This can result in a prolonged clotting time, elevated INR
and aPTT, but fibrinogen levels and fibrinogen degradation
products are within the normal range. The INR, in
particular, may be grossly elevated, occasionally >12.
However, without a full clotting laboratory, this may be
hard to ascertain, and the whole blood clotting time
might be prolonged in these patients, though a clot
should eventually form, unlike true defibrination
coagulopathy, as discussed earlier.
Experience has shown that persistent ooze from the bite
site or elsewhere is not likely as a result of venom
induced direct anticoagulation, again, different to
defibrination coagulopathy. Brown Snakes, Tiger Snakes,
Taipans and other species causing defibrination do not
cause this direct anticoagulation, as discussed earlier.
Antivenom is very effective at rapidly reversing direct
anticoagulation coagulopathy. Usually one vial of
antivenom will suffice.
3.14.3 Snakebite myolysis
This occurs most commonly after bites by Tiger Snakes,
Rough-scaled Snakes and Mulga Snakes/King Browns,
but may also occur occasionally after Taipan bites, while
bites by Red-bellied Black Snakes and Spotted/Blue-
bellied Black Snakes may result in low level myolysis
(CK 500–3,000IU).
It is the result of widespread direct damage to striated
muscle cells, resulting in complete muscle cell breakdown
within 1–3 days, though damage probably commences
within 1–3 hours of venom reaching the muscle. Full
recovery is possible, but will take 4+ weeks.
The key diagnostic indicators are myoglobinuria (easily
mistaken for haematuria) and a dramatic rise in plasma CK.
The latter may reach figures much greater than
100,000IU. In addition, patients complain of generalised
muscle pain, with tender muscles.
The secondary effects of myolysis are renal failure and
massive hyperkalaemia, which can be very difficult to
control and has proven lethal.
Once myolysis is established it is uncertain if antivenom
will reverse damage, but in severe cases it may be worth
trying further large doses of specific antivenom.
3.14.4 Snakebite neurotoxic paralysis
Presynaptic neurotoxic flaccid paralysis may occur after
bites by Tiger Snakes, Rough-scaled Snakes,
Copperheads, Taipans, rarely Brown Snakes.
It usually first manifests as ptosis, 1–3+ hours after the
bite, with potential progression to partial ophthalmoplegia,
complete ophthalmoplegia, fixed dilated pupils, dysarthria,
dysphagia, peripheral weakness, culminating in
PAGE 24 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
respiratory paralysis, though it may take 24+ hours to
reach this final stage. Once complete paralysis is
established it may take days, weeks or longer to reverse
sufficiently for the patient to survive off a ventilator.
Antivenom will not reverse well established presynaptic
paralysis.
Pure postsynaptic neurotoxic flaccid paralysis may occur
after bites by Death Adders, resulting in similar, but often
more rapid progression of symptoms and signs. This form
of paralysis is usually reversible if sufficient antivenom is
given. Neostigmine may also reduce the degree of paralysis.
3.14.5 Follow-up of snakebite patients
All patients with systemic envenoming should be
followed up over 6 months, with particular concern for
serum sickness over the first 14 days.
Consider giving a 7-day course of oral steroids as prophylaxis
if more than 25 mLs of antivenom has been given.
It is important to follow up all patients with initially trivial
or no apparent envenoming, especially if discharged less
than 24 hours post-bite, to ensure late onset envenoming
is not missed. In particular, look for late onset neurotoxic
envenoming, myolysis (not if proven Brown Snake bite)
and renal damage.
3.15 Management of the severely illpatient where diagnosis ofsnakebite is obscure
If the patient presents with unexplained onset of
collapse, convulsions, bleeding, paralysis, rhabdomyolysis
(e.g. muscle breakdown, myoglobinuria), or renal failure,
in a setting where snakebite might have occurred (e.g. in
rural areas, or gardens, paddocks, long grass in urban
areas), and particularly in children who may give no
history of exposure to snakes, then include snakebite in
the differential diagnosis.
Useful tests to establish if there has been a snakebite
include:
■ Examine patient on exposed areas for bite marks or
scratches.
■ Whole blood clotting time or coagulation studies to
establish if there is a coagulopathy.
■ Check for myolysis manifested by dark or red urine
indicative of myoglobinuria (positive for “blood” and
so may be mistaken for haematuria), elevated CK
(>1000).
■ Test for venom in urine using SVDK.
■ If in doubt discuss with a Clinical Toxicologist or
Toxicologist at the NSW Poisons InformationCentre on 131126 or your local Critical Care Referral
Network.
3.16 Management of the patient withno evidence of envenomation
3.16.1 Relevant history
■ Was a snake seen to bite (?multiple bites) OR were
the circumstances such that a bite might have
occurred?
■ When did the patient get bitten (elapsed time)?
■ Description of snake if possible (colour, length).
■ Geographic location the incident occurred (snakes in
the area).
■ Timing and type of first aid and activity after the bite.
■ Determine if there has been any evidence of
envenoming; specifically ask about headache,
nausea, vomiting, abdominal pain, blurred or double
vision, slurring of speech, muscle weakness,
respiratory distress, bleeding from the bite site or
elsewhere, passing dark or red urine, local pain or
swelling at the bite site, pain in lymph nodes
draining the bite area (axilla or groin), loss of
consciousness, convulsions.
■ Relevant past history; specifically allergy or past
exposure to antivenom, atopic history, renal, cardiac,
or respiratory disease.
3.16.2 Examination
Assess for:
■ Evidence of a bite (if there is an adequate first aid
bandage in place, cut it away from over the bite site,
keeping bandage away from area adjacent to skin
(DO NOT WASH WOUND; SWAB FOR VENOMDETECTION) looking for evidence of multiple bites,
or venom movement (i.e. swollen or tender draining
lymph nodes).
■ Neurotoxic paralysis (ptosis or drooping eyelids,
diplopia or double vision, dysarthria or slurred
speech, limb weakness, respiratory distress).
■ Coagulopathy (bleeding from bite site or elsewhere).
■ Muscle damage (muscle tenderness, pain on
movement, weakness, urine colour).
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 25
3.16.3 Investigations
■ Whole blood clotting time in a glass tube OR
■ Complete blood picture (CBP/FBE/FBC)
■ Coagulation studies (PT/INR, aPTT, Fibrinogen, d-
dimer/XDP/FDP)
■ Electrolytes (especially K++), renal function, CK (for
myolysis)
If envenomation is evident then refer to the relevant
section in these guidelines and the Snakebite
Management Chart (Figure 13: page 20).
If envenomation is not evident then the patient will still
need admission to hospital for observation overnight,
preferably to a high intensity nursing area, ensuring that
nursing staff are instructed to regularly check for signs of
emerging envenomation, in particular early signs of
paralysis (e.g. ptosis, diplopia, etc). (See Appendix 3.)
NOTE: There is no point in leaving first aid in place if the
patient is well and in hospital and the hospital is able to
treat snakebite (i.e. has the appropriate antivenom
available). The first aid bandage and splint merely delays
venom absorption, it does not inactivate venom, and
delay in removing first aid will delay onset of definitive
treatment of snakebite.
PAGE 26 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines